Generating electrical power is the typical goal of developing geothermal energy resources. Electrical energy is generated by converting the thermal energy of a geothermal fluid. Although the typical temperature of a geothermal resource (e.g., 500.degree. F. or 260.degree. C.), does not allow a high thermodynamic conversion efficiency, the large amount of geothermal fluids produced from some geothermal resources permits commercially feasible power generation.
A typical geothermal electrical power conversion facility or power plant includes production wells extracting the geothermal fluid from an underground geothermal resource, surface production facilities supplying a hot vapor under pressure (e.g., collection pipelines and steam separator/flash vessels if the geothermal fluid is a hot brine), a power conversion means extracting work (e.g., expanding the steam in a turbine-generator), a condenser for condensing the expanded vapor, and a source of coolant supplying the condenser (e.g., a cooling tower). Alternatively, a "binary" working fluid can be vaporized by the produced geothermal fluids and the binary vapor expanded in a turbine (instead of the geothermal fluid itself). Because of relatively high capital costs and difficulties in quickly changing geothermal production flowrates, the typical geothermal power plant operates at full load as much as possible, i.e., as a base load unit.
However, the demand for electric power is not constant over time, and storage of large amounts of electric power may be impractical. For example, night-time consumption patterns are different from the daylight consumption patterns. These changes in daily consumption patterns require other types of power plants, such as oil and gas fired steam units, to dispatch or load follow. Still other power plants are required to provide seasonal or peaking power (e.g., units operating only a few tens or hundreds of hours per year). Because these other types of power plants which accommodate demand changes cannot have their capital costs spread over as many kilowatt-hours as a baseload plant, capital intensive devices to improve efficiency are typically not present. The result is typically high fuel (and other operating) costs per unit of produced power.
What is needed is a more efficient method of producing power from geothermal resources that will better distribute capital costs and accommodate demand changes. This type of facility would avoid the need for several different types of power plants, decrease overall costs, and increase the usefulness of geothermal resources as a source of commercial geothermal power.